The present invention relates to the field of ophthalmology, particularly the topical treatment of ocular allergies. Most particularly, the present invention relates to ophthalmic compositions comprising 1-(2-ethoxyethyl)-2-(4-methyl-1-homopiperazinyl)-benzimidazole, otherwise known as emedastine, and its ophthalmically acceptable acid addition salts and methods for their use.
Allergic conjunctivitis is frequently characterized by ocular pruritus (itching), erythema (inflammatory redness), edema and tearing. This condition is one of the most frequently treated by ophthalmologists, optometrists and allergists. To date, treatment has been primarily through the use of topically applied histamine H.sub.1 antagonists in combination with .alpha.-agonists. See, for example, the following articles:
1. Miller, J. and E. H. Wolf, "Antazoline phosphate and naphazoline hydrochloride, singly and in combination for the treatment of allergic conjunctivitis--a controlled, double-blind clinical trial." Ann. Allergy, 35:81-86 (1975). PA1 2. Vandewalker, M. L. et al., "Efficacy of Vasocon-A and its components with conjunctival provocation testing (CPT)" J. Allergy Clin. Immunol., 83:302 (1989). PA1 3. Abelson, M. B. et al., "Effects of topically applied ocular decongestant and antihistamine." Am. J. Ophthalmol 90:254-257 (1980).
Recent studies indicate that the antihistamine levocabastine exhibits clinical activity in patients with allergic conjunctivitis without the addition of a vasoconstrictor. See, Dechant, K. L. and K. L. Goa, "Levocabastine. A review of its pharmacological properties and therapeutic potential as a topical antihistamine in allergic rhinitis and conjunctivitis." Drugs 41:202-224 (1991). In addition, it has recently been demonstrated that H.sub.1 antagonists are effective in relieving conjunctival injection (hyperemia) and erythema, as well as pruritus. See, Berdy, G. J. et al., "Allergic conjunctivitis: A survey of new antihistamines." J. Ocular Pharmacol. 7:313-324 (1991).
Although there are many different antihistamines available for systemic treatment of allergies and related ailments, many such antihistamines are not suitable for topical ophthalmic use because of limited ocular bioavailability. For example, terfenadine (Seldane.RTM., made by Marion Merrell Dow), astemizole (Hismanal.RTM., made by Janssen Pharmaceutica) and loratadine (Claritin.RTM., made by Schering) all have good systemic activity; however, terfenadine has little or no local ocular activity, and astemizole and loratadine each have greatly reduced local ocular activity (as compared to their systemic activity). A need therefore exists for an antihistamine having good local ocular activity and having minimal side effects.